The present invention relates to a pair of conjugating rotors for screw compressor in which the male rotor can drive the female rotor to rotate by the designed profiles. By means of the gap between the teeth of the male rotor and female rotor, fluid will be sucked in. And, by means of the shifting of the contacting point between the male rotor and female rotor, the fluid can be compressed into a high-pressure and high-speed state. The compression ratio can be raised to 2.about.15. If the fluid is oil or air, the compressed oil or air can be used to drive other mechanisms such as a control valve or a hydraulic cylinder. If the fluid is a coolant, the coolant can be compressed by the compressor and becomes a high-pressure coolant. This high-pressure coolant can be applied to an air-conditioner or a refrigerator. An excellent compressor must have three characteristics, which include high energy transfer efficiency, low vibration noise and low electricity consumption.
In order to achieve these three objects mentioned above, the male rotor and female rotor must be designed with special profiles. Theoretically, the movement transmission between the teeth of the male and female rotors is based on the theory of conjugating surfaces. For example, the power transmission of the conventional gear is based on the theory of conjugating surfaces. That is, once the profile of one of the male and female rotors is determined, the other rotor must be generated in accordance with the theory of conjugating surfaces. In the field of gear manufacture, such procedure is called generating method.This is just like traditional milling procedure. When a milling tool mills a work piece, except the milling tool's self-rotation at high speed, the milling tool also moves along a preset curve. After which, the remaining curved surface left on the work piece that is the so-called generated surface. In the present invention, the generating method is utilized. More specifically, the spiral outer surface of one of the rotors should be designed first. Second, the profiles of the tooth sections of the male rotor and female rotor of the screw compressor are designed. Then, in accordance with the generating method, the other profiles of the female and male rotors conjugating with the tooth sections are generated and sequentially connected with each other. Finally, such rotors can enhance the energy transfer efficiency, reduce the vibration noise and lower the power consumption.
The profiles of the male and female rotors of the conventional screw compressor are respectively composed of several curves. The presently used curves include circular curves, elliptic curves, etc. The circular curve has high transmissibility (such as good pressure angle) and good simplicity of curve so that it is advantageous in easy design and easy manufacturing. So, the circular curve is widely used. Parabolic curve and hyperbolic curve are relatively complicated. Elliptic curve is relatively poor. Therefore, these curves are not widely used. Polynomial curve had been designed and used in the past. The profiles of the rotors of the screw compressor of the present invention arc composed of multiple curves including circular curves, curves generated by circular curves and point generated curves.